Easiest Way to Replace All Characters in Even Positions in a String.

Easiest way to replace all characters in even positions in a string.

It is easily done with a regular expression:

echo preg_replace('/(.)./', '$1 ', $str);

The dot matches a character. Every second character is replaced with a space.

How to replace even values in string with ASCII value?

You are almost there, you simply need to build the resulting string.
Strings are immutable, so replacing would create a new String each time.
I would suggest a StringBuilder for this task, but you can also do it manually.

The result would look like this:

public static void main(String[] args) {
    String str = "ABCDEF";
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < str.length(); i++) {
        if (i % 2 != 0) {
            int m = str.charAt(i);
            sb.append(m); // add the ascii value to the string
        } else {
            sb.append(str.charAt(i)); // add the normal character
        }
    }
    System.out.println(sb.toString());
}

Output:

A66C68E70

How to replace odd/even chars in string with spaces in Java?

You could simply split the input on the space and process each work individually. You could then use a StringJoiner to piece together the result, for example...

String s = "go to med!!";
String alphabetS = "abcdefghijklmnopqrstuvwxyz";

String[] words = s.split(" ");
StringJoiner sj = new StringJoiner(" ");
for (String word : words) {
    StringBuilder sb = new StringBuilder(word);
    for (int i = 0; i < sb.length(); i++) {
        char currChar = sb.charAt(i);

        int idx = alphabetS.indexOf(currChar);
        if (idx != -1) {
            if (i % 2 == 1) {
                sb.setCharAt(i, '*');
            }
        }

    }
    sj.add(sb.toString());
}
System.out.println(sj.toString());

which outputs

g* t* m*d!!

could this be done without using arrays - just with char and string methods?

Instead of relying on i, you need a separate counter, which tracks which point your up to and which can be used to ignore invalid characters, for example

String s = "go to med!!";
String alphabetS = "abcdefghijklmnopqrstuvwxyz";

StringBuilder sb = new StringBuilder(s);
int counter = 0;
for (int i = 0; i < sb.length(); i++) {
    char currChar = sb.charAt(i);

    int idx = alphabetS.indexOf(currChar);
    if (idx != -1) {
        if (counter % 2 == 1) {
            System.out.println("!!");
            sb.setCharAt(i, '*');
        }
        counter++;
    }

}
System.out.println(sb.toString());

which still outputs

g* t* m*d!!

String builder replace elements at even indexes in string

Some things I will correct, but @Nikolai Dmitriev already pointed some of them out.

1. The n is needed, even though @Nikolai Dmitriev said it's not. Since you want to replace it with its ASCII value. However, you can shorten it to String a = String.valueOf((int) c); or even get rid of the c and just straight up use `String a = String.valueOf((int) sb.charAt(i));
2. You are using sb.replace(char start, char end, String str); while the function should accept sb.replace(int start, int end, String str);. To correct this, just use sb.replace(i, i + 1, a);. Notice that you use end = i + 1 because the StringBuilder replace function end value is exclusive (not including).
3. Initialize result at the end. The variable has a scope of inside the for loop if you do it inside, and since you want to return it, you would want to initialized it after you finish replacing all even-indices.

How to replace characters in a string in python

name = "ABCDEFGH"
nameL = list(name)

for i in range(len(nameL)):
    if i%2==1:
        nameL[i] = '$'

name = ''.join(nameL)
print(name)    

How would I remove letters at an even position throughout a string in Java?

Try this.

• It uses a regex that takes two chars at a time and replaces them with the 2nd, thus removing every other one.
• the (.) is a capture group of 1 character.
• $1 is a back reference to it.

   String s = "abcdefghijklmnopqrstuvwxyz";
   s = s.replaceAll("(?s).(.)?", "$1");
   System.out.println(s);

Prints

bdfhjlnprtvxz

per Andreas suggestion, I preceded the regex with a flag that lets . match returns and linefeeds.

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